In co-pending parent patent application Ser. No. 380,792 (now U.S. Pat. No. 3,907,966) entitled Nickel Recovery, a process for recovering nickel from ammoniacal leach solutions containing nickel, copper and other metal values is disclosed. In that process, metal values such as copper are first extracted leaving a raffinate containing nickel. The nickel in the raffinate is then extracted with an organic extractant such as an oxime. After leaving the nickel extraction circuit, the nickel on the nickel loaded extractant is stripped with a highly concentrated ammonium salt solution to yield a strip concentrate from which nickel or nickel oxide is recoverable without electrolytic treatment.
Although essentially all of the copper is extracted in the copper extraction circuit, a small amount of copper, i.e. approximately 0.05 grams per liter remains with the nickel in the raffinate leaving the copper extraction circuit. This trace amount of copper in the raffinate entering the nickel extraction circuit builds up on the organic used to extract nickel in the nickel extraction circuit to a level where a small amount of copper is stripped in the nickel stripping circuit along with the nickel. Indeed, when the process reaches steady state, copper builds up in the organic to a level where an amount of copper is stripped in the nickel stripping circuit that is equal to the amount of copper that is extracted in the nickel extraction circuit. Of course, the copper that is stripped in the nickel stripping circuit remains with the nickel as a nickel product contaminant.
Another disadvantage of having copper loaded on the organic that is used to extract nickel in the nickel extraction circuit is that the presence of copper on the organic adversely effects the nickel extraction efficiency as well as the nickel loading capacity of the organic.